1. Technical Field
The invention relates to a touch system and a touch method. Particularly, the invention relates to an optical touch system supporting multi-touch and a touch point calculation method thereof.
2. Related Art
Along with widespread use of windows operating system Windows 7, all-in-one (AIO) personal computers (PCs) with a highlighted multi-touch function gradually become a mainstream in the market. In the conventional resistive, capacitive and back projection touch screens, the capacitive touch screen has a best touch effect, though the cost thereof is most expensive and increases along with a size of the touch screen, so that usage effectiveness of the capacitive touch screen is inadequate.
In order to seek an alternatives, an optical touch screen that uses optical lenses to detect a touch position is developed, which has advantages of low cost and good accuracy, etc., and is competitive in the market, so that it becomes another choice of the large size touch screen.
In the optical touch screen, a plurality of optical lenses are configured at an edge of the screen to capture images of user's finger operated on the screen, and a position of finger shadow in the captured image generated due to that the finger interrupts the light is analysed to obtain relative angles between a finger touch point and the optical lenses, and then according to a known distance between the optical lenses, an actuate position of the touch point can be calculated through triangulation.
The aforementioned method for determining a finger position according to the finger shadow has already achieved high accuracy in application of detecting single-finger touch. However, in application of detecting multi-finger touch, since a distance between the fingers is rather close, in certain angles, positions of different fingers appeared in the images captured by the optical lenses are overlapped, which leads to a result that the optical touch screen misjudges the multi-finger operation as a single-finger operation.
For example, FIG. 1 is a schematic diagram of a conventional optical touch screen detecting a finger touch. Referring to FIG. 1, in the conventional optical touch screen, optical lenses 12 and 13 are respectively configured at corners (for example, an upper left corner and an upper right corner) of a same side of a screen 11, and the optical lenses 12 and 13 all face to the other side of the screen 11, so as to capture finger gestures of the user operated on the screen 11. When the user uses two fingers 14 and 15 to touch the screen 11, since a distance between the two fingers 14 and 15 is close, the fingers 14 and 15 are overlapped in the field of vision of the optical lenses 12 and 13, and as a result, the optical touch screen may misjudge the above operation as a single-finger operation of a finger 16 shown as dot lines, so that a recognition rate of multi-touch of the optical touch screen is decreased.